U.S. Pat. No. 4,245,920, entitled "Interconnectable Molecular Models and a Fastener for Connecting Same" discloses a mechanical fastener for joining two plugs in coaxial alignment and in a plurality of relative orientations. The fastener is particularly adapted for use in joining models of molecular constituents to assemble models of larger molecular structures. Models of molecular constituents are disclosed which incorporate a plug having a generally cylindrical shank extending along an axis corresponding to a chemical bond and at least one tab projecting outwardly from the surface of the shank. Broadly, the fastener comprises a hollow housing which includes a first and a second end wall and a side wall extending between the two end walls. The end walls and the side wall define a cavity within the housing. Each end wall has a plug-receptacle opening passing through it shaped and dimensioned to receive a plug. The surface of each end wall which faces the cavity has a plurality of grooves therein extending radially outwardly from the plug-receptacle opening and spaced apart azimuthally around the opening. The grooves are oriented and configured to accommodate the tab from the plug.
U.S. Pat. No. 4,348,190, entitled "Interlocking Molecular Model System" discloses a molecular model system in which a first component representative of an atom includes at least one elongated shank that has a cylindrical section of one cross-sectional area with an inwardly extending shoulder and an outwardly extending abutment located between the shoulder and the part of the component that represents the nucleus. The molecular model system further includes a fastener component that has a hollow tubular portion longitudinally slotted at one end and having an axial length that represents a predetermined portion of a covalent radius of the atom. The inner surface at one end of the slotted end portion extends inwardly to be hooked behind the shoulder to interlock with the shank.